1. Field of the Invention
The present invention relates to an automatic assembling method and apparatus for a differential gear which comprises a differential arrangement or mechanism of an automobile, for instance.
2. Description of the Prior Art
Conventionally, a differential gear that makes up the differential gear arrangement or mechanism of an automobile has been assembled manually by worker(s), or by a known assembling method, for instance, as shown in Japanese Patent Laying-Open No. Hei 6-156338 (1994).
In the manual assembly method performed manually by worker(s), a pair of side gears are positioned along a predetermined one of three orthogonal axial directions within a differential case, and a pair of spherical washers and a pair of pinion gears are inserted from a pair of openings formed in the differential case in another axial direction so as to mesh with the gear teeth of the side gears and the pinion gears. Thereafter, while rotating the side gears and moving the pinion gear and the spherical washer to a position shifted by 90 degrees in phase, central axes of the pinion gear and the spherical washer are fitted in the remaining one axial direction. Then, at this position, by inserting a shaft from a shaft hole directly to a shaft insertion bore at central shaft portions of each of the pinion gears and the spherical washers like a spear, the differential gear is thereby assembled.
On the other hand, in the case of Japanese Patent Laying-Open No. Hei 6-156338 (1994) mentioned above, the pair of side gears are positioned rotatably in the differential case, and edge portions of a pair of pinion support devices are inserted into the shaft insertion bores of the spherical washers and the pinion gears from the spherical washer side so as to hold them at each internal round surface thereof. At the same time, the gear teeth of the side gears and the pinion gears are meshed with each other, and then the edge portions of the pinion support devices are pulled out from the pinion gears. Thereafter, by means of a pinion pushing device, the pinion gear and the spherical washer are urged to a position shifted by 90 degrees in phase, and then the shaft is inserted therein to by aligning the shaft insertion bores formed in the central axial portions of the pinion gear and the spherical washer to the shaft hole of the differential case.
However, with the prior art, in particular the manual assembling method, there are drawbacks in that workers who are skilled in such tasks are necessitated and that it needs a large number of assembling processes.
In addition, in the case of Japanese Patent Laying-Open No. Hei 6-156338 (1994) mentioned above, the pinion gear and the spherical washer are supported by each of the pinion gear support devices from the spherical washer side (or differential case side). Therefore, it is necessary to open or relieve the holding by the pinion support devices so as to avoid interference between the pinion support devices and the differential case when moving the pinion gears and so on to the position shifted by 90 degrees in phase after meshing with the gear teeth of the pinion gears and the side gears. Therefore, it is impossible to move the pinion gears and so on to the predetermined positions without the provision of separate pinion pushing devices. Therefore, there is a drawback that the manufacturing equipment becomes complex and oversize.
Further, since pressure is applied at the gear teeth of the pinion gear, and further since the pinion gear meshes with the side gear thereby accompanying the rotation thereof when it is moved, there is therefore also a drawback in that the gear teeth of the pinion gear are easily damaged or broken.
Moreover, there may also be a drawback in that it is impossible to insert the shaft without holding the spherical washer at the proper position simultaneously while pushing the pinion gear, since the shaft insertion bores of the pinion gear and the spherical washer become misaligned when it is moved to the predetermined position.